U.S. patent application number 13/313868 was filed with the patent office on 2013-06-13 for water reservoir for a steam generation system and method of use thereof.
This patent application is currently assigned to ALSTOM TECHNOLOGY LTD.. The applicant listed for this patent is Bruce W. Wilhelm. Invention is credited to Bruce W. Wilhelm.
Application Number | 20130145998 13/313868 |
Document ID | / |
Family ID | 47326141 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130145998 |
Kind Code |
A1 |
Wilhelm; Bruce W. |
June 13, 2013 |
WATER RESERVOIR FOR A STEAM GENERATION SYSTEM AND METHOD OF USE
THEREOF
Abstract
Disclosed herein is a system comprising an evaporator; a water
reservoir in fluid communication with the evaporator; the water
reservoir being located upstream of the evaporator; and a first
steam drum in fluid communication with the evaporator; the first
steam drum being located downstream of the evaporator; where the
water reservoir is operative to supply feedwater to the evaporator
while maintaining a predetermined water level in the first steam
drum.
Inventors: |
Wilhelm; Bruce W.; (Enfield,
CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wilhelm; Bruce W. |
Enfield |
CT |
US |
|
|
Assignee: |
ALSTOM TECHNOLOGY LTD.
Baden
CH
|
Family ID: |
47326141 |
Appl. No.: |
13/313868 |
Filed: |
December 7, 2011 |
Current U.S.
Class: |
122/448.4 ;
122/451R |
Current CPC
Class: |
F22B 37/78 20130101;
F22B 37/22 20130101 |
Class at
Publication: |
122/448.4 ;
122/451.R |
International
Class: |
F22B 37/46 20060101
F22B037/46; F22D 5/26 20060101 F22D005/26 |
Claims
1. A system comprising: an evaporator; a water reservoir in fluid
communication with the evaporator; the water reservoir being
located upstream of the evaporator; and a first steam drum in fluid
communication with the evaporator; the first steam drum being
located downstream of the evaporator; where the water reservoir is
operative to supply feedwater to the evaporator while maintaining a
predetermined water level in the first steam drum.
2. The system of claim 1, wherein saturated water from the steam
drum is mixed with feed water in the water reservoir.
3. The system of claim 1, where the first steam drum is in fluid
communication with the water reservoir.
4. The system of claim 1, where the first steam drum comprises a
first water level indicator; the first water level indicator being
operative to shut off the flow of feed water from the water
reservoir to the evaporator when the water level in the first steam
drum exceeds a desired level.
5. The system of claim 1, where the steam drum comprises a second
water level indicator; the second water level indicator being
operative to facilitate the flow of feed water from the water
reservoir to the evaporator when the water level in the steam drum
is reduced below the desired level.
6. The system of claim 1, where the water reservoir comprises a
water level indicator; the water level indicator being operative to
stop heat input to the steam generator to protect the system from
overheating.
7. The system of claim 1, where the system comprising the water
reservoir is shorter than an equivalent system that does not
contain the water reservoir when both systems utilize an equivalent
drum diameter, hold up time and produce an equivalent amount of
steam.
8. The system of claim 1, further comprising a second steam drum;
where the second steam drum is in fluid communication with the
water reservoir.
9. The system of claim 8, where the second steam drum is in fluid
communication with the evaporator.
10. The system of claim 9, where the second steam drum is in fluid
communication with the water reservoir.
11. A method comprising: discharging feed water from a water
reservoir to an evaporator; where the water reservoir lies upstream
of the evaporator and is in fluid communication with the
evaporator; and discharging water and steam from the evaporator to
a first steam drum; where the evaporator lies upstream of the first
steam drum and in fluid communication with the first steam drum;
where an amount of water discharged from the water reservoir to the
evaporator is effective to increase the water level in the first
steam drum to a desired level.
12. The method of claim 11, where the discharging the feed water
from the reservoir to the evaporator occurs when the load on the
evaporator changes to produce an increased or decreased ratio of
steam to water.
13. The method of claim 11, further comprising discharging water
and steam from the evaporator to the second steam drum.
14. The method of claim 11, further comprising discharging water
and steam from the first steam drum to the second steam drum.
15. The method of claim 11, further comprising discharging water
and steam from the second steam drum to the first steam drum.
Description
TECHNICAL FIELD
[0001] This disclosure relates to a water reservoir for a steam
generation system and to methods of use thereof.
BACKGROUND
[0002] Drum-type steam generation systems generally comprise three
major components: an evaporator, a superheater and an economizer.
The different components are put together to meet the operating
needs of the unit. Some drum-type steam generation systems may not
have a superheater or may include additional components such as
reheaters.
[0003] The FIG. 1 is a depiction of an exemplary prior art
evaporator system 100 of a drum-type steam generator that comprises
an evaporator 102 and a steam drum 104. The steam drum 104 is in
fluid communication with the evaporator 102. The steam drum 104 is
both downstream and upstream of the evaporator 102, i.e., they lie
in a recycle loop. In the operation of the evaporator system 100 of
the FIG. 1, when the load on the evaporator 102 changes more water
is drawn from the steam drum 104. For example, if there is a need
for a greater amount of steam than that which was previously
desired, the water level in the steam drum 104 drops. Feed water is
then introduced to the steam drum 104 to maintain the predetermined
operating water levels.
[0004] The steam drum 104 is therefore sized based on the steam
needs for the drum-type steam generator. However, when additional
requirements such as the water hold time exceeds the normal steam
drum 104 water storage level for a single drum, it is desirable to
increase the size of the steam drum 104. The water hold time (also
sometimes termed the "holdup time") is based on the measured liquid
volume between normal water level (NWL) and the lowest (also
sometimes referred to as the "lo-lo") water level trip. The lowest
water trip level is the minimum level at which there will be no
danger of overheating any part of the steam generator during
operation. This lowest water level is generally about 30
centimeters (about 1 foot) above the bottom of the drum, but varies
according to drum diameter.
[0005] The normal water level is set below the high water level, as
needed for water level measurement accuracy, margin to control
feedwater flow and steam purity. In general, the location of normal
water level results in about 15 seconds to 30 seconds of water
volume (depending upon the flow rate) between the normal water
level and the water level trip. The volume of water contained in
the drum at these different heights can be calculated using simple
formulas for the area of a circular segment.
[0006] One manner of increasing the water hold time of a single
steam drum is to increase the length and/or the diameter of the
drum. However, this may not be a viable option where space
availability is limited. The use of larger diameter drums increases
shell wall thicknesses to accommodate internal pressures. Thicker
walled vessels however generally use longer heat up times when
compared with thinner walled vessels resulting slower transient
during start-up and/or load changes.
[0007] It is therefore desirable to increase the water hold time of
the steam drum without incurring additional costs associated with
increasing space or with increasing the wall thickness.
SUMMARY
[0008] Disclosed herein is a system comprising an evaporator; a
water reservoir in fluid communication with the evaporator; the
water reservoir being located upstream of the evaporator; and a
first steam drum in fluid communication with the evaporator; the
first steam drum being located downstream of the evaporator; where
the water reservoir is operative to supply feedwater to the
evaporator while maintaining a predetermined water level in the
first steam drum.
[0009] Disclosed herein too is a method comprising discharging feed
water from a water reservoir to an evaporator; where the water
reservoir lies upstream of the evaporator and is in fluid
communication with the evaporator; and discharging water and steam
from the evaporator to a first steam drum; where the evaporator
lies upstream of the first steam drum and in fluid communication
with the first steam drum; where an amount of water discharged from
the water reservoir to the evaporator is effective to increase the
water level in the first steam drum to a desired level.
BRIEF DESCRIPTION OF THE FIGURES
[0010] FIG. 1 is a depiction of an exemplary prior art evaporator
system that comprises an evaporator and a steam drum;
[0011] FIG. 2 depicts an exemplary system that comprises an
evaporator, a steam drum and a water reservoir that are in fluid
communication with one another; and
[0012] FIG. 3 depicts an exemplary system that comprises an
evaporator, two steam drums and a water reservoir that are in fluid
communication with one another.
DETAILED DESCRIPTION
[0013] Disclosed herein is an evaporator system that comprises an
evaporator, a steam drum and a reservoir. The reservoir is used for
holding additional water that is supplied to the evaporator and
allows for an increase in the water hold time in the system.
Disclosed herein too is a method of increasing the water hold time
by providing a water reservoir, which holds water that is supplied
to the evaporator when the water level in the steam drum decreases
from the normal level. The normal level will hereinafter be
referred to as a predetermined level. The evaporator system
disclosed herein may be part of a drum-type steam generation system
with natural or forced circulation such as heat recovery generation
system, steam generation solar receivers, fossil fuel fired steam
generation systems and other systems where an increase in the
volume of the steam drum is desired to increase water hold up time,
but where there are space limitations.
[0014] FIG. 2 depicts a system 200 that comprises an evaporator
202, a steam drum 204 and a water reservoir 206 that are in fluid
communication with one another. The evaporator 202 is disposed
upstream of the steam drum 204 and downstream of the water
reservoir 206. Feed water is fed into the water reservoir 206 via a
valve 208. In one embodiment, the valve 208 is a flow control
valve. The water from the water reservoir 206 is fed to the
evaporator 202, where it is converted into steam and water. The
water and steam are then fed from the evaporator 202 into the steam
drum 204, where the steam is separated from the water. The steam is
discharged to a superheater or to a turbine to generate energy,
while the water in the steam drum 204 is recycled to the water
reservoir 206 where it mixes with the feed water before being fed
to the evaporator 202.
[0015] Both the steam drum 204 and the water reservoir 206 are
equipped with level sensors to detect when desired liquid levels
(e.g., water levels) deviate from desired values. The steam drum
204 comprises a first water level indicator, which is activated
when the water level increases above a certain level (e.g., a high
water level indicator), drops below a certain desired level (e.g.,
a low water level indicator) and control the feed water to the
reservoir to maintain the predetermined water level. The
predetermined water level lies between the high water level and the
low water level. The water reservoir 206 also comprises a second
water level indicator, which is activated when the water level
decreases below a certain desired level (e.g., a low water level
trip). The water level indicators may be floats, a manometer (e.g.,
a distilled water column or a mercury column), conductivity probes
or the like, or a combination thereof.
[0016] In one embodiment, in one method of operating the
evaporation system 200 of the FIG. 2, when the demand or load on
the evaporator 202 changes such that the ratio of steam to water
generated in the evaporator 202 is increased, the level of water in
the steam drum 204 may decrease below the desired level. When the
water level decreases below the predetermined level as indicated by
the water level indicator, feed water flow to the water reservoir
is increased. The increased water flow from the water reservoir 206
is introduced into the evaporator 202 to comply with the
requirement for additional steam, while at the same time
compensating for the loss of water from the steam drum 204. On the
other hand, when the water level in the steam drum 204 increases
above the desired level, feed water flow to the water reservoir is
decreased. The reduced water flow from the water reservoir 206 is
introduced into the evaporator 202 to comply with the requirement
for a lower rate of steam-water flow into the steam drum 204. In
one embodiment, when the water level in the water reservoir 206
decreases below the predetermined level, water is fed into the
water reservoir 206 via the valve 208 to maintain the water level
to the predetermined level.
[0017] The presence of the water reservoir 206 in the evaporation
system 200 can thus be used to minimize space requirements in at
least one direction. In one embodiment, the system comprising the
water reservoir is shorter than an equivalent system that does not
contain the water reservoir when both systems utilize an equivalent
drum diameter, hold up time and produce an equivalent amount of
steam.
[0018] If the evaporation system 200 were devoid of the water
reservoir 206, the steam drum 204 would have to be longer, which
depending on the arrangement may be difficult to fit into a
confined space or the diameter would have to be increased. In
addition, as drum diameter increases the thickness of the walls of
the steam drum 204 would have to be increased to the point where
the stresses in these walls would increase significantly. The use
of a water reservoir 206 prevents these problems.
[0019] In another embodiment depicted in the FIG. 3, the
evaporation system 200 comprises two steam drums--a first steam
drum 204 and a second steam drum 214 in fluid communication with
the water reservoir 206 and the evaporator 202. The first steam
drum 204 and the second steam drum 214 may be in fluid
communication with one another. Steam and water from the evaporator
202 can be discharged to the first steam drum 204 and to the second
steam drum 214. In one embodiment, water and steam from the first
steam drum 204 can be discharged to the second steam drum 214. In
another embodiment, water and steam from the second steam drum 214
can be discharged to the first steam drum 204.
[0020] While the FIG. 3 depicts two steam drums 204 and 214, the
system can have more than two drums. In other words, the
evaporation system 200 may comprise a plurality of steam drums in
fluid communication with the water reservoir 206 and the evaporator
202. By using two steam drums 204 and 214, the length and size of
the steam drums can further be minimized. The two steam drums 204
and 214 function in conjunction with the water reservoir 206 and
the evaporator 202 in the same manner as the single steam drum 204
in the FIG. 2.
[0021] When the water level decreases below the desired level as
indicated by the water level indicator, water from the water
reservoir 206 is introduced into the evaporator 202 to comply with
the requirement for additional steam, while at the same time
compensating for the loss of water in the steam drum 204 or the
steam drum 214. If the level of water in the steam drums 204 or 214
decreases below the desired level then additional feedwater is
supplied to the water reservoir 206 via the valve 208.
[0022] It will be understood that, although the terms "first,"
"second," "third" etc. may be used herein to describe various
elements, components, regions, layers and/or sections, these
elements, components, regions, layers and/or sections should not be
limited by these terms. These terms are only used to distinguish
one element, component, region, layer or section from another
element, component, region, layer or section. Thus, "a first
element," "component," "region," "layer" or "section" discussed
below could be termed a second element, component, region, layer or
section without departing from the teachings herein.
[0023] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting. As
used herein, the singular forms "a," "an" and "the" are intended to
include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" and/or "comprising," or "includes" and/or "including"
when used in this specification, specify the presence of stated
features, regions, integers, steps, operations, elements, and/or
components, but do not preclude the presence or addition of one or
more other features, regions, integers, steps, operations,
elements, components, and/or groups thereof.
[0024] Furthermore, relative terms, such as "lower" or "bottom" and
"upper" or "top," may be used herein to describe one element's
relationship to another element as illustrated in the Figures. It
will be understood that relative terms are intended to encompass
different orientations of the device in addition to the orientation
depicted in the Figures. For example, if the device in one of the
figures is turned over, elements described as being on the "lower"
side of other elements would then be oriented on "upper" sides of
the other elements. The exemplary term "lower," can therefore,
encompasses both an orientation of "lower" and "upper," depending
on the particular orientation of the figure. Similarly, if the
device in one of the figures is turned over, elements described as
"below" or "beneath" other elements would then be oriented "above"
the other elements. The exemplary terms "below" or "beneath" can,
therefore, encompass both an orientation of above and below.
[0025] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
disclosure belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0026] While the invention has been described with reference to a
preferred embodiment and various alternative embodiments, it will
be understood by those skilled in the art that changes may be made
and equivalents may be substituted for elements thereof without
departing from the scope of invention. In addition, many
modifications may be made to adapt a particular situation or
material to the teachings of the invention without departing from
the essential scope thereof. Therefore, it is intended that the
invention not be limited to the particular embodiment disclosed as
the best mode contemplated for carrying out this invention, but
that the invention will include all embodiments falling within the
scope of the appended claims.
* * * * *